Vinyl fluoride polymers and vinylidene fluoride polymers are thermoplastic polymers which have a combination of useful properties and, in particular, a high chemical inertness, an excellent resistance to weathering and ultra-violet rays and a good impermeability to gases and vapours. Because of this, they have many uses in very diverse fields, and in particular in protection from corrosion. Nevertheless, they have the disadvantage of being relatively expensive, which is likely to limit their applications. A suitable means of reducing the cost of shaped articles of vinyl or vinylidene fluoride polymers comprises using these polymers in the form of multi-layered thermoplastic structures (films, sheets, plates, tubes and the like), in which they are associated with bulk thermoplastic polymers which impart to them, in addition, their own properties and advantages, such as, for example, mechanical strength. However, said fluorinated polymers adhere very poorly to other thermoplastic polymers, and especially to alpha-olefin polymers, so that it is generally necessary to resort to adhesives, most frequently polymeric adhesives, to ensure an adhesive bond between these fluorinated polymers and other thermoplastic polymers.
French Pat. No. A-1,484,153 (THE DOW CHEMICAL CO) recommends the bonding of a layer of polyolefin to a layer of a fluorinated hydrocarbon polymer with the aid of a polymeric adhesive consisting of, preferably, a copolymer of ethylene and vinyl acetate containing about 13 to 35% by weight of vinyl acetate.
It has now been found that multi-layered structures of the prior art in which a polyolefin is bonded to a fluorinated hydrocarbon polymer with the aid of a copolymer of ethylene and vinyl acetate containing 13 to 35% by weight of vinyl acetate are sensitive to delamination at the fluorinated polymer layer.